An arrangement for accumulating sample substances for spectroscopical purposes by a flow injection technique is known from a publication by Olsen et al in the journal, "The Analyst", vol. 108, 905-917. Water, a buffer liquid in the form of ammonium acetate, and an eluting liquid in the form of nitric acid are pumped into parallel hose conduits by a peristaltic pump. An injection valve is provided in the hose conduit into which the water is pumped. The injection valve has a passage and a sample loop, which is arranged to be optionally connected to the flow in the hose conduit. When the passage is connected to the hose conduit, a flow of sample liquid is passed through the sample loop so that the sample loop is filled with sample liquid. After switching over the injection valve, the sample loop filled with sample liquid is connected to the hose conduit conducting the water flow so that the sample liquid is carried along by the flow of water. Either the water or the sample liquid is mixed with the buffer liquid and flows through the ion exchanger when a valve arrangement is in its first valve position, namely from the first end of the ion exchanger column to the second end thereof. The second end communicates with a waste outlet port. In the first valve position of the valve arrangement, the eluting liquid flows to a nebulizer and is sprayed into the flame of an atomic absorption spectrometer. An accumulation of the sample in the ion exchanger column follows. Subsequently, the valve arrangement is switched over to a second valve position. In this second valve position, the water--and the ammonium acetate hose conduits --communicate with the waste outlet port. The second end of the ion exchanger column communicates with the hose conduit conducting the eluting liquid. The first end of the ion exchanger column communicates with the nebulizer of the atomic absorption spectrometer. The eluting liquid flows through the ion exchanger column in the reverse direction compared to the previous flow direction and elutes the accumulated elements of the sample which are to be determined into the nebulizer and thus into the burner of the atomic absorption spectrometer.
By virtue of a publication by Hartenstein et al in by Zhaolun Fang et al in "Analytica Chimica Acta" 200 (1987), 35-49, an arrangement is known in which a first sample liquid with an associated buffer liquid, and a second sample liquid with an associated buffer liquid, are each pumped by a first peristaltic pump. The sample liquids are mixed with the associated buffer liquids in conduit coils which are connected downstream to the peristaltic pump. The mixture of sample liquid and buffer liquid obtained in this way is passed to a first valve. In a first valve position of the first valve, the sample and buffer liquids are passed to a first end of an associated ion exchanger column. Each of the second ends of the ion exchanger columns communicate with a waste outlet port. Then, the two ion exchanger columns are parallelly charged with sample liquid, the sample being accumulated within the column. A second peristaltic pump pumps an eluting liquid and water. In the first position of the valve, the water is passed to the nebulizer of a plasma burner. In this first position of the valve, the eluting liquid communicates with a waste outlet port. In the second position of the valve, the eluting liquid passes to the second end of an ion exchanger column, the first end of which then communicates with the nebulizer. The ion exchanger column to which the eluting liquid is supplied is selected by a changeover valve.
By the use of two ion exchanger columns which are parallelly charged, the analyzing period of time can be approximately halved. During the charging of the ion exchanger column, water instead of the eluting liquid is passed to the nebulizer. The water rinses the nebulizer and stabilizes the plasma.
In the prior art method, the eluting liquid is passed with the eluted, accumulated sample to a nebulizer which sprays the liquid into the flame of an atomic absorption spectrometer.
It is also known to use a flow injection method in atomic absorption spectroscopy by inserting a sample, which is pretreated, into a furnace for thermoelectric atomization ("ANALYST" vol. 109 (March 1984), 323-325). However, the pretreated sample from the flow injection system is first passed into an open sample vessel and is dosed from this sample vessel into the furnace of the atomic absorption spectrometer. Thus, the substantial advantages of the flow injection technique, such as the entire occlusion of the sample from the environment and the possibility of treating very small sample amounts, are lost.
In a publication by Hamann, Meier, and Kettrup in "Fresenius Zeitschrift fur analytische Chemie", 1989, vol. 334, pages 231 to 234, there is described the determination of phenoxycarboxylic acid herbicides using high pressure liquid chromatographies. Therein, the herbicides are enriched in a precolumn.
A publication by Jackson and Haddad in the "Journal of Chromatography", vol. 439 (1988), pages 37 to 48, describes a flow injection arrangement including anion preconcentration, wherein the preconcentrated sample is passed through a UV absorption detector.
German Patent No. 2,900,066, corresponding to U.S. Pat. No. 4,294,126, describes a sample feeder in which the samples are arranged in sample receptacles at a turntable. A take up tube takes up sample liquid from the sample receptacles by suction and delivers the same through a sample infeed opening into a furnace for electro-thermally atomizing the sample. A measuring light beam of an atomic absorption spectrometer is passed through the furnace.